Short answer: Ketoconazole has a half-life of about 2 hours, then 8 hours (tablets). Levels peak 1 to 2 hours (tablets) after a dose. People vary, so treat these as estimates.
Ketoconazole is an azole antifungal. It is sold as Nizoral 1% anti-dandruff shampoo over the counter, as a 2% prescription shampoo and cream, and as 200 mg tablets. The tablets carry a boxed warning for liver injury and are reserved for serious fungal infections when other treatments fail; use of the shampoo for hair loss is off-label.
Also known as: Nizoral.
Nizoral Anti-Dandruff is a 1% shampoo sold over the counter. Ketoconazole 2% shampoo and 2% cream are prescription products. Ketoconazole tablets are 200 mg.
The Nizoral 1% Drug Facts label is for flaking, scaling and itching from dandruff, in adults and children 12 and older: lather, rinse, repeat, every 3 to 4 days for up to 8 weeks, then as needed. The prescription 2% shampoo label is for tinea versicolor, a fungal skin rash, as one 5-minute application. That label says ketoconazole was not detected in the blood of people who shampooed with it for months.
The tablets are different. Their boxed warning says they are not for nail, skin or Candida infections and should be used only when other antifungals are not available or tolerated, because oral ketoconazole has caused serious liver injury, including deaths and liver transplants, and raises levels of many drugs, some to the point of dangerous heart rhythms. The label dose is 200 mg once a day, up to 400 mg, usually for 6 months; it lowers the body's own steroid hormone output at 400 mg and above. It is not used with liver disease.
Use of the shampoo for hair loss is off-label. In a small 1998 study (Piérard-Franchimont), 2% ketoconazole shampoo improved hair density and the share of growing-phase hairs about as much as 2% minoxidil with a plain shampoo; the authors said a larger controlled study was needed. See also topical minoxidil.
The ketoconazole tablet label says a 200 mg tablet taken with a meal peaks in 1 to 2 hours, and that it leaves the blood in two phases: a half-life of 2 hours over the first 10 hours, and 8 hours after that. These figures are for the tablets. The 2% shampoo label says ketoconazole was not detected in blood after months of shampooing.
Numbers shown are taken from the source above. Half-life varies from person to person.
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